The Fine Winning Margin

Aerospace engineering might reasonably conjure up impressions of rocket scientists. But at Royal Melbourne Institute of Technology (RMIT), the Aerospace Engineering Department has many of its projects planted firmly on the ground, or not far above it.

The most famous project of all and one that is now beginning to return on its investment is the Superbike. Lachlan Thompson and his associates at the RMIT Aerospace Engineering Department in Port Melbourne have been instrumental in a joint venture with the Australian Institute of Sport (AIS) to design and manufacture of the RMIT-AIS Superbike. This machine dominates in world cycling and has 22 world cycling championship titles to its credit.

The RMIT-AIS Superbike is constructed from a carbon fibre and resin composite material and is stiffer and lighter than a metal frame of any kind.

The project began modestly in 1992 when changes the rules of competitive cycling made it feasible to begin work on radical new designs. The first Superbikes were raced to victory in the UCI World Cup in the USA in 1994 and have continued to win ever since.

Traditional bicycle construction tended to be based on experience and the availability of standard materials in well-recognised form. Research showed that the most efficient gains were to be made in the area of frame , forks and handlebars. The other components of the bicycle were retained in more-or-less traditional form.

The aim was to reduce weight and improve aerodynamics in the selected components. This is done by using lighter materials, reducing the volume of material and shaping the material to reduce drag. The basics anthropomorphics of a bicycle are well-known. Further input from the AIS and Olympic cycling coaches and riders, much more information was gathered on the previously unknown quantities and relationships between machine and human in cycling. Gathering the analytical data revealed startling results in terms of the demands placed on the machines by the riders, The peak loads imposed on bike components amaze even very experienced machinery designers.

The resulting Superbike design is a combination of a monocoque (single piece) frame with a new style of front fork and handlebar configuration. It is constructed from a carbon fibre and resin composite material and is stiffer and lighter (around 5kg) than a metal frame of any kind. The frame is moulded in an aluminium die with an inflatable core. The production process is very expensive to set up and begin production. With limited funds for R& D, there is no provision to tool up just for a prototype to try out. With costs of up to A$100,000 to produce the moulding dies, it is essential that they are only made once and able to go straight into production. The icing on the cake of the Superbike project is that the bike is also suitable for mass production, i.e. it can be made in adequate numbers for a reasonable price to satisfy world demands for this kind of machine. The Superbike is produced under license by Bike Technologies in Melbourne and a production frame/fork-handlebar combination sells for between A$2,300-3,500 bare.

The Need for CAD

Employing computers in the Superbike project seems an obvious requirement. The reasons are easily defined in very practical terms.

• CAD allows the rapid creation of potential design solutions, thus enabling a number of potential solutions to be developed concurrently.

• Creating design data with CAD software means the data is instantly and accurately available in a form acceptable to aerodynamic and finite element analysis software as well as other kinds of software that might well be used to analyse the design or enhance the presentation of proposed designs.

• Digital data created in a CAD program also simplifies and speeds the creation of production tools through direct output to CNC machines.

CAD output can also be directed to rapid prototyping devices such as the stereolithographic machine at RMIT’s own rapid prototyping bureau. Accurate scale models created with these "3D printers" can be surface finished, machined and tested in wind tunnels and water tanks for further analysis, without any need for traditional pattern or modelmaking processes, eliminating time delays and inherent inaccuracies in the models.

CADKEY wireframe model of the Superbike front fork.

The Demands on CAD

Computer -aided design carries a tradition of steep learning curves and dedicated application by its users in order to become productive. A requirement of the CAD implementation in the Superbilke project was that it should be easy and fast to learn. Few of the people working on the project had been extensively exposed to CAD in a production environment. A long ramp up period to get productive was simply unacceptable.

The computer lab at the aerospace engineering department provides access to almost every kind of engineering software available. An evaluation of the available options resulted in the selection of CADKEY. In practice CADKEY has found to be ideally suited to the task. Designers were able to begin work on real projects, after only a couple of days of informal hands-on familiarisation. You might well ask what kind of background these designers have that allows such a rapid uptake of a particular software package.

CADKEY rendering of the Superbike front fork.

They come form a range of technical disciplines including industrial design and mechanical design. All are comfortable using computers, but none had any prior professional experience using CAD. Offering a personal judgment made in the short time I visited the department, I have to say the people I met there are highly motivated and have very resourceful attitudes to their projects.

In the same way that is should be fast to learn, a requirement was also that it be easy use. Although the Superbike is not large, it does contain some very sophisticated shapes and blends connecting them. Equally sophisticated methods of modelling such shapes are required. CADKEY offered a very good range of modelling processes that appealed to the designers. In practice, the variety of modelling options becomes invaluable. Designers found that modelling some shapes requires a very creative approach to using the software tools available. CADKEY’s various options provide several different ways to reach the same modelling result, giving designers the flexibility to reach their ultimate destination by various direct means. Sometimes modelling a surface even requires a hybrid approach where a temporary construction model is created and the final shape modelled using virtual controls to achieve the desired end result.

The ability to produce the kinds of shapes required, was an important criteria. Many of the shapes and transitions are very complex and because of the scale or the structure and the nature of the materials, need to be modelled very precisely. All design work on the Superbike is done in 3D. The facility CADKEY delivers on this requirement is mentioned above. The ease with which newcomers to CAD can quickly become productive in 3D is attributed in a large part to the tools CAD provides and the easy access it provides to these tools.

CADKEY is used in conjunction with FastSURF and ToolChest add-on packages for processing output to CNC machinery. This is an essential extra component for the design team. Other than that there is no add-on software required or used with CADKEY. Designers use direct output from CADKEY for analysis with STRAND FEA software and aerodynamic analysis software developed in-house.

The complete frame bike is beyond analysis in software due to its complexity. Parts of the frame are extracted for analysis and checking and practical analysis is done on scale models in wind tunnel testing.

Time to produce a basic bike design in CADKEY with full precision is around 5 days. This is a major improvement on the months it could take to create a model in clay or resin, digitise the real model and then massage it into an acceptable digital form.

The Gains

The RMIT-AIS Superbike is a remarkable piece of collaborative engineering design and vision. The success of the project is due to the diligence and foresight of the people working on the project, the materials available in our time and the tools available to apply the available knowledge to the materials.

Naturally computers are an essential part of the technology employed and CADKEY is an important part of the computing effort that has created the Superbike.